Mg<inf>x</inf>Mn<inf>2-x</inf>B<inf>2</inf>O<inf>5</inf> Pyroborates (2/3 ≤ x ≤ 4/3): High Capacity and High Rate Cathodes for Li-Ion Batteries
Chemistry of Materials
American Chemical Society
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Glass, H., Liu, Z., Bayley, P., Suard, E., Bo, S., Khalifah, P., Grey, C., & et al. (2017). Mg<inf>x</inf>Mn<inf>2-x</inf>B<inf>2</inf>O<inf>5</inf> Pyroborates (2/3 ≤ x ≤ 4/3): High Capacity and High Rate Cathodes for Li-Ion Batteries. Chemistry of Materials, 29 3118-3125. https://doi.org/10.1021/acs.chemmater.7b00177
MgMnB2O5, Mg2/3Mn4/3B2O5, and Mg4/3Mn2/3B2O5 pyroborates have been prepared via a ceramic method. When charging MgMnB2O5 vs Li, all of the Mg2+ can be removed, and with subsequent cycles, 1.4 Li ions, corresponding to a capacity of 250 mAhg-1, can be reversibly intercalated. This is achieved at a C/25 rate with 99.6% Coulombic efficiency. Significant capacity is retained at high rates with 97 mAhg-1 at a rate of 2C. Continuous cycling at moderate rates gradually improves performance leading to insertion of 1.8 Li, 314 mAhg-1 with a specific energy of 802 Whkg-1, after 1000 cycles at C/5. Ex situ X-ray and neutron diffraction demonstrate the retention of the pyroborate structure on cycling vs Li and a small volume change (1%) between the fully lithiated and delithiated structures. Mg2/3Mn4/3B2O5 and Mg4/3Mn2/3B2O5 are also shown to reversibly intercalate Li at 17.8 and 188.6 mAhg-1, respectively, with Mn ions likely blocking Mg/Li transport in the Mg2/3Mn4/3B2O5 material. The electrochemical ion-exchange of polyanion materials with labile Mg ions could prove to be a route to high energy density Li-ion cathodes.
External DOI: https://doi.org/10.1021/acs.chemmater.7b00177
This record's URL: https://www.repository.cam.ac.uk/handle/1810/265042